1. Field of the Invention
The present invention relates to a liquid-jet head, in which pressure generating chambers that communicate with nozzle orifices ejecting liquid droplets are partially constituted by vibration plates, piezoelectric elements which are provided above the pressure generating chambers having the vibration plates interposed therebetween, and the liquid droplets are ejected with the displacement of the piezoelectric elements, and relates to a liquid-jet apparatus. More particularly, the present invention relates to an ink-jet recording head that ejects ink as the liquid and to an ink-jet recording apparatus.
2. Description of the Related Art
Two methods ate put into practical use in an ink-jet recording head, in which pressure generating chambers that communicate with nozzle orifices ejecting ink droplets are partially constituted of vibration plates, these vibration plates are deformed by piezoelectric elements to pressurize ink in the pressure generating chambers, and the ink droplets are ejected from the nozzle orifices. One is a recording head that uses piezoelectric actuators of a longitudinal vibration mode, which expand and contract in the axis direction of the piezoelectric elements, and the other is a recording head that uses piezoelectric actuators of a flexural vibration mode.
In the former, a volume of each pressure generating chamber can be changed by abutting the end surface of the piezoelectric element against the vibration plate, thus enabling manufacturing of a head suitable to high density printing. On the contrary, while possible, a difficult process is required in cutting and dividing the piezoelectric element in a comb tooth shape in accordance with the array pitch of the nozzle orifices and work of positioning and fixing the cut and divided piezoelectric elements to the pressure generating chambers. Thus, there is a problem of a complex manufacturing process.
On the other hand, in the latter, the piezoelectric elements can be fabricated and installed on the vibration plate by a relatively simple process of adhering a green sheet of a piezoelectric material while fitting a shape thereof to that of the pressure generating chambers and baking the green sheet. However, a certain area of the vibration plate is required due to use of the flexural vibration, and thus there is a problem that a high density array of the piezoelectric elements is difficult.
Meanwhile, in order to solve such a disadvantage of the latter recording head, a recording head is proposed, in which an even piezoelectric material layer is formed over the entire surface of the vibration plate by a deposition technology, the piezoelectric material layer is divided into a shape corresponding to that of pressure generating chambers by a lithography method, and piezoelectric elements are formed so as to be independent of one another for each pressure generating chamber (refer to, for example, Japanese Patent Laid-Open No. Hei 5(1993)-286131, FIG. 3, Paragraph (0013)).
As a structure of such an ink-jet recording head as described above, a structure has been known, which includes: a passage-forming substrate having at least two rows of pressure generating chambers communicating with nozzle orifices; and a joining plate joined to a piezoelectric element side of the passage-forming substrate, on which a drive circuit for driving piezoelectric elements is mounted, wherein the piezoelectric elements are electrically connected to the drive circuit through penetrated holes provided in the joining plate (refer to, for example, Japanese Patent Laid-Open No. 2000-296616, FIG. 20, Paragraph (0161) to (0163)).
Specifically, in such an ink-jet recording head as described above, two rows of the piezoelectric elements 202 are provided in regions corresponding to the rows of the pressure generating chambers 201 as shown in FIG. 7. Moreover, each piezoelectric element 202 is extended from a region opposing the pressure generating chamber 201 to the peripheral wall of the reservoir 203 and is sandwiched between the passage-forming substrate 204 and the reservoir-forming plate (joining plate) 205. Furthermore, the penetrated holes 206 are provided for each row of the pressure generating chambers 201 on the reservoir 203 sides of the reservoir-forming plate 205, that is, in regions opposing the peripheral walls of the pressure generating chambers 201. Then, the drive circuit 207 mounted on the approximate center portion of the reservoir-forming plate 205, that is, on a region corresponding to a space between the rows of the piezoelectric elements 202, is electrically connected to the respective piezoelectric elements 202 through the penetrated holes 206 provided individually on both sides of the drive circuit 207 by the bonding wires 208.
However, though the manufacturing cost of the conventional ink-jet recording head is controlled to be relatively low since the recording head is constructed to drive two rows of the piezoelectric elements with one drive circuit, the following problem is inherent therein. The penetrated holes are formed individually on the both sides of the drive circuit, which cause the necessity of making the passage-forming substrate and the joining plate relatively large, and cause a difficulty in the miniaturization of the head,
Particularly, when the head is attempted to be miniaturized by arraying the pressure generating chambers in high density, there is a problem of difficulty in securing regions where the plurality of penetrated holes are formed.
Note that such a problem as described above needless to say occurs in other liquid-jet heads ejecting liquids other than ink, similarly to the ink-jet recording head ejecting ink.
In consideration of such circumstances as described above, it is an object of the present invention to provide a liquid-jet head that is capable of arraying the pressure generating chambers in high density and achieving miniaturization thereof.
A first aspect of the present invention that attains the foregoing object is a liquid-jet head comprising: a passage-forming substrate including at least two rows of pressure generating chambers communicating with a nozzle orifice and being defined by a plurality of compartment walls; and piezoelectric elements composed of a lower electrode, a piezoelectric layer and an upper electrode, the piezoelectric element being provided on one surface side of the passage-forming substrate with vibration plates interposed therebetween, characterized in that a joining plate joined onto the piezoelectric element side of the passage-forming substrate is provided, on which a drive circuit for driving the piezoelectric elements is mounted, a penetrated hole penetrating the joining plate in a thickness direction is provided in a portion corresponding to a space between the rows of the pressure generating chambers of the joining plate, an extracted wiring extracted from individual the piezoelectric elements is extended to the portion corresponding to the penetrated hole, and the extracted wiring and the drive circuit are electrically connected to each other with conductive wires extended through the penetrated hole.
In the first aspect, the region where the penetrated hole is formed can be reduced, and therefore, the pressure generating chambers can be arrayed in high density, and the head can surely be miniaturized.
A second aspect of the present invention is the liquid-jet head according to the first aspect, in which the plurality of drive circuits for driving the piezoelectric elements individually for each of the rows of the pressure generating chambers are provided, and the drive circuits are mounted on both sides of the penetrated hole.
In the second aspect, the drive circuits and the extracted wiring can be connected relatively easily to each other with the connection wiring, and manufacturing cost thereof can be suppressed relatively low.
A third aspect of the present invention is the liquid-jet head according to any one of the first and second aspects, in which the joining plate includes a piezoelectric element holding portion for hermetically sealing a space secured in a region facing towards the piezoelectric elements.
In the third aspect, the breakage of the piezoelectric elements due to an external environment is prevented.
A fourth aspect of the present invention is the liquid-jet head according to any one of the first to third aspects, in which the joining plate includes a reservoir portion constituting at least a part of a liquid chamber common to the pressure generating chambers.
In the fourth aspect, the joining plate also serves as a reservoir-forming plate, and therefore, it is not necessary to provide the reservoir-forming plate separately, and the head can be miniaturized.
A fifth aspect of the present invention is the liquid-jet head according to any one of the first to fourth aspects, in which the drive circuit is a semiconductor integrated circuit.
In the fifth aspect, the drive circuit can be mounted on the joining plate relatively easily.
A sixth aspect of the present invention is the liquid-jet head according to any one of the first to, fifth aspects, in which the pressure generating chambers are formed by anisotropic etching for a single crystal silicon substrate, and each layer of the piezoelectric element is formed by deposition and lithography methods.
In the sixth aspect, the large amount of the liquid-jet heads having high-density nozzle orifices can be manufactured relatively easily.
A seventh aspect of the present invention is a liquid-jet apparatus comprising the liquid-jet head according to any one of the first to sixth aspects.
In the seventh aspect, a liquid-jet apparatus can be realized, in which jet density of liquid droplets is improved, and miniaturization is achieved.